As a method of purifying aluminum or an aluminum alloy, there has been a conventionally proposed technology of adding an element that forms a complex compound (which will be referred to as a complex compound forming element hereinafter) with an element serving as an impurity into a molten metal of aluminum or an aluminum alloy containing the element serving as an impurity to precipitate the element serving as an impurity as the complex compound in the aluminum molten metal, causing rectifying rotation to the aluminum molten metal to subject the complex compound to centrifugal separation based on a difference in specific gravity, and collecting the complex compound on a wall surface of an agitated vessel to be removed (Patent Document 1). This method is used for recycling of, e.g., an aluminum resource and, according to this method, when an element serving as an impurity in an aluminum molten metal is specified in advance and a corresponding complex compound forming element, e.g., the element serving as an impurity is Fe or Si, Mn, Zr, or Ca is added and the temperature is maintained at 640 to 700° C. to enable precipitation of a complex compound.
On the other hand, as a purifying method utilizing electromagnetic processing, a method of producing an electromagnetic force in a central (inner) direction in a cylindrical vessel having a molten metal therein by a fixed alternating magnetic field to collect inclusions having low electric conductivities near a vessel wall has been proposed (Non-patent Literature 1). Further, information that a method of applying a strong magnetic field to a molten metal to perform magnetic separation of inclusions was theoretically analyzed and its effectiveness was confirmed from an experiment has been also reported (Non-patent Literature 2).
Patent Document 1: Japanese Patent Application Laid-open No. 229055-1999
Non-patent Literature 1: Fumitaka Yamao, Kensuke Sassa et al., “Separation of Inclusions in Liquid Metal Using Fixed Alternating Magnetic Field”, Tetsu-to-Hagane, vol. 83, No. 1, 1997
Non-patent Literature 2: Norihisa Waki, Kensuke Sassa et al., “Magnetic Separation of Inclusions in Molten Metal Using a High Magnetic Field”, Tetsu-to-Hagane, vol. 86, No. 6, 2000